The present invention relates to a gas insulated switch gear, particularly, a gas insulated switch gear with a potential transformer suitable for improving reliability.
A gas insulated switch gear includes a combination of a plurality of components such as a breaker, disconnecting switches, grounding switches, a potential transformer, and others, and a power supply conductor for electrically connecting these components to each other in a closed enclosure charged with insulating gas.
The gas insulated switch gear is superior in size reduction, insulation performance, and safety and therefore, is widely used in electric plants such as substations. As shown in Japanese Laid-Open Patent Publications 10-75513(1998), 60-187217(1985) and 60-18390(1985), the conventional gas insulated switch gear having a potential transformer includes connection conductors, disconnectors connected to the conductors, cable sealing ends connected to the disconnectors, an arrestor, one end of which is connected to the disconnectors and the cable sealing ends; a single phase potential transformer, one terminal of which is connected between the disconnector and cable sealing end disposed in one phase of three phases.
The potential transformer is enclosed in an airtight chamber together with a plurality of other components of the line unit, and therefore, the potential transformer is exposed to air when assembled to the gas insulated switch gear. A problem of reduced the reliability is caused because water and dust are attached to the windings of the potential transformer in proportion to the exposure duration to the air.
Additionally, when current flows through a conductor mounted in the line unit, a magnetic field occurs. The induced voltage is generated at the secondary side of the potential transformer by causing the magnetic field to interlink with the core of the potential transformer. As a result, the output is distorted.